The present invention generally relates to fluid flow meters for valves and pipelines. More particularly, the present invention relates to a flow meter based on the principle of vortex which is capable of being inserted into small insertion holes of the waterworks valve, pipeline, etc. and which is capable of measuring very low fluid flow rates.
In fluid dynamics, it is well known that when fluid encounters an obstacle placed in the axis of the fluid flow, it divides and creates small eddies or vortices on alternate sides of the obstacle. The generation of a succession of alternating turbulent waves is called a Karman vortex street. The frequency of detachment of the vortices, or the generation of the vortices, is directly proportional to the velocity of the fluid.
Insertion vortex flow meters are based upon this phenomenon. The vortices detachment generates zones of variable pressure that form small pressure surges and can be detected using a sensor positioned at a site downstream of the obstacle.
Currently, such current flow meters have limitations. The existing flow meters function in a permanent turbulent flow range defined by a Reynolds number above 5000, generally equivalent to flow velocities greater than 1.5 feet/second (0.5 m/s). This flow regime establishes a stable Karman vortex street, which is easily detectable by unsophisticated electronics.
While measuring fluid flows greater than 0.5 m/s and defined by a Reynolds number above 5000 covers the vast majority of industrial applications, in the potable water field supply systems (waterworks systems) such systems are generally designed for a maximum of speed of about 3 feet/second (about 1 m/s) and have a much lower minimum velocity. This is especially the case when there is low consumption, such as during the nighttime hours, where the water can practically be stopped with little fluid flow in the waterworks system. In fact, there can be many time periods or instances when the water flow is between 0.2 m/s and 0.5 m/s. Such low fluid flows create vortex waves having a much lower Reynolds number than 5000, and whose detection requires more sophisticated electronics and an appropriate algorithm which has heretofore been unavailable.
Another problem with current flow meters is the mechanical insertion of the flow meter into the pipeline. In order for the measurement cylinder of the flow meter to be oriented correctly and have sufficient space between the obstacle and the measurement sensor, a length of at least 1.5 inches (about 40 mm) is required. Accordingly, an insertion aperture or boss is needed in the control valve, butterfly valve, filter, joint, or portion of the pipe, etc. (collectively referred to herein as valve and/or pipeline) with a minimum diameter of 1.5 inches (40 mm) and larger in order to be able to mechanically insert a flow meter into the valve or pipeline.
In the field of industrial valves, much of the equipment, including valves and pipelines, are frequently designed in a standardized way with extra tapped apertures, for example, for the ease of mounting accessories and the like. When the tapped apertures are not used, they are normally plugged by a threaded and sealed cap. When using the tapped aperture, the cap is removed and provides accommodation for, as an example, a manometer. In many of the valves and pipelines used in the waterworks industry, the tapped apertures have a diameter of less than 1 inch (less than 30 mm). The majority of the tapped apertures have a diameter of 0.5 inches (approximately 13 mm), in particular for pipeline equipment between 2 inches and 20 inches (50 mm to 500 mm) in diameter, while other tapped apertures have a diameter of 0.75 inches (approximately 19 mm) or 1.0 inch (approximately 25 mm). However, the size and elbow-shaped configuration of existing flow meters requires a tapped aperture or boss with a minimum diameter of 1.5 inches (at least 38 mm). Accordingly, there is a continuing need for a vortex flow meter which is capable of being inserted into valves and pipelines having insert apertures or bosses with a diameter of less than 1.0 inch (approximately 25 mm) or even into such insertion apertures having a diameter of only 0.5 inches (approximately 13 mm). What is also needed is such a vortex flow meter which can detect and accurately measure fluid flow velocities less than 1.5 feet/second (0.5 m/s). The present invention fulfills these needs, and provides other related advantages.